If at all possible I would split your time between the Ren and the Marriott. The Ren is downtown with no beach and the downtown activites will be exhausted within 2 days. The Marriott has some of the best shore snorkelling on the island right off their beach and is SO much more relaxing. Renting a car is a must. Both the Ren and the Marriott have free self parking for guests and criving aroudn the island is a must. Visit Sol Food in WestPunt for lunch (only open F, S and S) and Shete Boca National Park on your way there.